Date: 12/30/18 1:10 pm From: <clearwater...> Subject: [obol] Re: Winter Barn Swallow in Central Oregon
The attached plot (produced from the WestMap climate analysis website) might be helpful for considering the effects of climate change on winter survival of wayward Barn Swallows in central Oregon.
The plot shows mean temperatures for the month of January in Deschutes County, from 1920 through 2017.
During the 70-year period from 1920 through 1990, the mean January temperature exceeded 34 F only twice (in 1934 and 1953). Since 1990 -- approximately when the predicted effects of anthropogenic climate change began to become discernible from background variations -- this value has been exceeded six times. Four of those times were in the past seven years.
In other words, relatively warm months of January have been much more frequent in the past couple of decades.
Cold months of January have also been less frequent. The mean January temperature has dipped below 27 F only three times since 1990 (1 in 6 years), whereas prior to 1990 this happened in about 1 out of 4 years.